Fix typo in Windows Build Instructions

In the "Get the code" section, shouldn't it be "fetch chromium"? As
it is unlikely that people who build Chromium on Windows want to target
iOS.

Also this is my first patch submission, so I think I also need to add my
name to the AUTHORS file.

BUG=

Review-Url: https://codereview.chromium.org/2545313002
Cr-Commit-Position: refs/heads/master@{#436203}

AUTHORS

@@ -721,6 +721,7 @@ William Xie <william.xie@intel.com>
 Xiang Long <xiang.long@intel.com>
 Xiangze Zhang <xiangze.zhang@intel.com>
 Xiaolei Yu <dreifachstein@gmail.com>
+Xiaoyin Liu <xiaoyin.l@outlook.com>
 Xinchao He <hexinchao@gmail.com>
 Xing Zhang <xzhang@adobe.com>
 Xinghua Cao <xinghua.cao@intel.com>

docs/windows_build_instructions.md

@@ -99,7 +99,7 @@ Run the `fetch` tool from `depot_tools` to check out the code and its
 dependencies.
 
 ```shell
-$ fetch ios
+$ fetch chromium
 ```
 
 If you don't want the full repo history, you can save a lot of time by